POS0588 SEASONALITY OF FLARE AND REMISSION PATTERNS IN RHEUMATOID ARTHRITIS: A POPULATION-BASED COHORT STUDY
Authors: R. Javed, C. S. Crowson, J. M. Davis, E. Myasoedova
Journal: Annals of the Rheumatic Diseases (2022)

Background Flare of rheumatoid arthritis (RA) disease activity is an important aspect of RA disease experience for patients with RA, associated joint damage and comorbidity. Major advancements in treatment of RA in recent decades resulted in improving trends in RA disease activity and increasing rates of remission. However, flares in RA remain common and some patients are still unable to achieve remission. Disease-modifying antirheumatic drugs have a major impact on controlling RA disease activity, minimizing the likelihood of flares. The effect of environmental factors on the pattern of flares and remissions in RA is less studied. Previous studies showed conflicting results regarding the likelihood of flare and remission occurrence across the seasons of the year. Objectives To assess the seasonal pattern in the occurrence of flares and remissions in a population-based cohort of patients with RA. Methods This retrospective population-based cohort study included patients with RA (age ≥30 years) who met 1987 ACR criteria in 1988-2007. A retrospective review of each clinical visit in the medical records was performed to ascertain flare or remission status. A flare was defined as an episodic worsening of RA disease activity that leads to initiation, change or increase of treatment. Remission was defined as the absence of disease activity based on a tender joint count of 0, a swollen joint count of 0 and an ESR less than 10 mm/h. Seasons were defined as: winter (Dec, Jan, Feb), spring (Mar, Apr, May), summer (June, July, Aug) and autumn (Sep, Oct, Nov). All subjects were followed until death, migration or July 1, 2012. Generalized linear models with random effects to account for multiple visits per patient were used for data analyses. Results The study included 650 RA patients (mean age 55.8 years; 69% female) with a mean follow up of 10.3 years. In a total of 17,323 clinical visits, patients were flaring in 2887 (17%) visits. The incidence of RA flares was 15% higher in the spring than in the winter (OR 1.15: CI: 1.02-1.29, p=0.045) after adjusting for age, sex and RA duration. There was no change in flare pattern between winter and summer or autumn. Remission rate did not differ between the seasons. (3df test p=0.65). Conclusion Patients with RA were more likely to experience flares in spring as compared to winter, and there were no differences in flare rates for the rest of the seasons. Remission rates were similar between the seasons of the year. The reasons for this seasonal effect on flare pattern is unknown, and the role of patient-related and environmental risk factors remains to be investigated. Our findings on the seasonality in flare occurrence can be used to inform patients about the risk of RA disease flares throughout the year. Disclosure of Interests Rabia Javed: None declared, Cynthia S. Crowson: None declared, John M Davis III Grant/research support from: Received research grant from Pfizer for rheumatoid arthritis., Elena Myasoedova: None declared.